Re: Bug reading a byn file for Canadian geoid model?

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I started a branch to fix it. Looks like there enough info in the byn
header.

On Wed, 15 Jul 2026, 20:00 Even Rouault, <[email protected]> wrote=
:

> Javier,
>
> I'd assume that code that assigns datums to have only been valid for the
> particular grids it was developped for. You'd better ignore any CRS
> information reported by the driver and override them from the
> documentation of the grid you're interested in
>
> Even
>
> Le 09/07/2026 =C3=A0 17:20, Javier Jimenez Shaw via gdal-dev a =C3=A9crit=
 :
> > Hi
> >
> > I am trying to read this file, in theory based in ITRF
> >
> https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/process/download-helper.p=
hp?file_id=3DGSD95
> > (there is another one based in NAD83xxx)
> >
> > However in with gdalinfo I see this:
> > "Warning 1: CRS EPSG:4140 is deprecated. Its non-deprecated
> > replacement EPSG:4617 will be used instead. To use the original CRS,
> > set the OSR_USE_NON_DEPRECATED configuration option to NO."
> >
> > EPSG:4140 https://spatialreference.org/ref/epsg/4140/
> > is NAD83(CSRS98), that is not ITRF, as far as I know.
> >
> > However in byndataset.h there is this line:
> >
> > constexpr int BYN_DATUM_0 =3D 4140;  /* ITRF2008 (GRS80 based WGS84) */
> >
> > https://github.com/OSGeo/gdal/blob/master/frmts/raw/byndataset.h#L168
> >
> > Are we parsing the header wrongly?
> >
> > There is some documentation in
> >
> https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/tools-outils/sample_doc_f=
iles/NRCan_Geoid_GridFormat_EN_2023.pdf
> > I think what I say above applies to the field 16, Datum.
> >
> > Thanks
> > Javier
> >
> > _______________________________________________
> > gdal-dev mailing list
> > [email protected]
> > https://lists.osgeo.org/mailman/listinfo/gdal-dev
>
> --
> http://www.spatialys.com
> My software is free, but my time generally not.
> LLMs contribute to global warming and brain rot.
>
>

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<div dir=3D"auto">I started a branch to fix it. Looks like there enough inf=
o in the byn header.</div><br><div class=3D"gmail_quote gmail_quote_contain=
er"><div dir=3D"ltr" class=3D"gmail_attr">On Wed, 15 Jul 2026, 20:00 Even R=
ouault, &lt;<a href=3D"mailto:[email protected]">even.rouault@spat=
ialys.com</a>&gt; wrote:<br></div><blockquote class=3D"gmail_quote" style=
=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding=
-left:1ex">Javier,<br>
<br>
I&#39;d assume that code that assigns datums to have only been valid for th=
e <br>
particular grids it was developped for. You&#39;d better ignore any CRS <br=
>
information reported by the driver and override them from the <br>
documentation of the grid you&#39;re interested in<br>
<br>
Even<br>
<br>
Le 09/07/2026 =C3=A0 17:20, Javier Jimenez Shaw via gdal-dev a =C3=A9crit=
=C2=A0:<br>
&gt; Hi<br>
&gt;<br>
&gt; I am trying to read this file, in theory based in ITRF<br>
&gt; <a href=3D"https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/process/dow=
nload-helper.php?file_id=3DGSD95" rel=3D"noreferrer noreferrer" target=3D"_=
blank">https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/process/download-hel=
per.php?file_id=3DGSD95</a><br>
&gt; (there is another one based in NAD83xxx)<br>
&gt;<br>
&gt; However in with gdalinfo I see this:<br>
&gt; &quot;Warning 1: CRS EPSG:4140 is deprecated. Its non-deprecated <br>
&gt; replacement EPSG:4617 will be used instead. To use the original CRS, <=
br>
&gt; set the OSR_USE_NON_DEPRECATED configuration option to NO.&quot;<br>
&gt;<br>
&gt; EPSG:4140 <a href=3D"https://spatialreference.org/ref/epsg/4140/" rel=
=3D"noreferrer noreferrer" target=3D"_blank">https://spatialreference.org/r=
ef/epsg/4140/</a> <br>
&gt; is=C2=A0NAD83(CSRS98), that is not ITRF, as far as I know.<br>
&gt;<br>
&gt; However in byndataset.h there is this line:<br>
&gt;<br>
&gt; constexpr int BYN_DATUM_0 =3D 4140; =C2=A0/* ITRF2008 (GRS80 based WGS=
84) */<br>
&gt;<br>
&gt; <a href=3D"https://github.com/OSGeo/gdal/blob/master/frmts/raw/byndata=
set.h#L168" rel=3D"noreferrer noreferrer" target=3D"_blank">https://github.=
com/OSGeo/gdal/blob/master/frmts/raw/byndataset.h#L168</a><br>
&gt;<br>
&gt; Are we parsing the header wrongly?<br>
&gt;<br>
&gt; There is some documentation in <br>
&gt; <a href=3D"https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/tools-outil=
s/sample_doc_files/NRCan_Geoid_GridFormat_EN_2023.pdf" rel=3D"noreferrer no=
referrer" target=3D"_blank">https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod=
/tools-outils/sample_doc_files/NRCan_Geoid_GridFormat_EN_2023.pdf</a><br>
&gt; I think what I say above applies to the field 16, Datum.<br>
&gt;<br>
&gt; Thanks<br>
&gt; Javier<br>
&gt;<br>
&gt; _______________________________________________<br>
&gt; gdal-dev mailing list<br>
&gt; <a href=3D"mailto:[email protected]" target=3D"_blank" rel=3D"n=
oreferrer">[email protected]</a><br>
&gt; <a href=3D"https://lists.osgeo.org/mailman/listinfo/gdal-dev" rel=3D"n=
oreferrer noreferrer" target=3D"_blank">https://lists.osgeo.org/mailman/lis=
tinfo/gdal-dev</a><br>
<br>
-- <br>
<a href=3D"http://www.spatialys.com" rel=3D"noreferrer noreferrer" target=
=3D"_blank">http://www.spatialys.com</a><br>
My software is free, but my time generally not.<br>
LLMs contribute to global warming and brain rot.<br>
<br>
</blockquote></div>

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